1. Field
One or more embodiments of the present invention relate to an optical device, and more particularly, to an optical image shutter.
2. Description of the Related Art
Optical image shutters transmit or block an optical image containing information according to a control signal. Optical shutters are essential optical modules widely used in image pickup devices, such as cameras, and display devices, such as liquid crystal displays (LCDs).
Optical shutters may be technically classified into a mechanical shutter used in a camera or the like, a liquid crystal shutter used in an LCD, a digital micromirror device used in a projection display device, a micro-electro-mechanical system (MEMS)-based spatial light modulator such as a grating light-valve, an intensifier used in a laser radar (LADAR) or a three-dimensional (3D) camera, and a semiconductor-based optical shutter.
In terms of working principles and shutter speeds, a mechanical shutter drives a lens shade by using an electro-magnetic motor and has a shutter time of 1 millisecond (ms) or so. A liquid crystal shutter is driven by the rotation of liquid crystal molecules and has a shutter time of several milliseconds. A MEMS-based spatial light modulator drives a fine structure with an electrostatic force and has an operation time of tens of microseconds (μs). An intensifier used in a 3D camera and a semiconductor-based optical shutter are driven by the photoelectric conversion of a semiconductor and have a shutter time of several nanoseconds (ns).
Light modulation devices rely on electro-optical effect in which a refractive index varies according to an electric field. Examples of light modulation devices relying on electro-optical effect include a Kerr cell using Kerr effect and a Pockel cell using Pockel effect.
However, Kerr cells and Pockel cells relying on electro-optical effect often use a bulk electro-optical crystal that requires a driving voltage of thousands of volts in order to obtain desired effect.